1. Field of the Invention
The present invention pertains to a method and apparatus for providing improved support for freshly inked sheet material in a printing press or the like.
2. Background Art
It has been traditional in the art of printing press apparatus and the like to provide devices for supporting freshly inked sheet material when transferring the material from one printing station to another or when handling the sheets as they are delivered from the press wherein said devices comprise wheels of relatively narrow width and characterized by having circumferentially spaced teeth. Such devices are known by the term skeleton wheels in the printing press art. The problems inherent in handling freshly inked printed sheets and the like by skeleton wheels have been longstanding. In order to minimize the contact area between the skeleton wheels and the printed sheet traditional thinking led to the provision of wheels in the form of relatively thin disks having a toothed or serrated circumference. However, these types of wheels have not overcome the problems of smearing and marring the inked surface of the sheet material due to sliding action between the material and the projections or serrations. Moreover, the attempts to minimize the surface area in contact with the sheet material has also resulted in actual indenting or dimpling of the material itself.
Various efforts have been made to overcome the disadvantages of thin disk skeleton wheels. One of the more successful approaches has been completely contrary to the concept of minimizing the surface area. This more recent development is disclosed and claimed in my U.S. Pat. No. 3,791,644 wherein I provide for a substantially cylindrical drum or roller coated with an improved ink repellent surface comprising a layer of polytetrafluoroethylene. Although this improved skeleton wheel has been commercially successful, with continuous use such as is common in many commercial printing operations, there is over a period of time a slight accumulation of ink on the surface of the wheel.
In high speed commercial printing equipment, for example, it has been determined that in order to provide satisfactory printing quality the surface of the coated wheel must be washed relatively frequently with a solvent to remove any ink accumulation. Moreover, it has also been determined that the TFE coated wheels do not provide a cushioning effect which is important for the tightly stretched sheet material as it engages and is supported by the skeleton wheel.
In accordance with the present invention the problems with the prior art thin disk and other type skeleton wheel concepts have been overcome with a skeleton wheel of relatively great width and with an improved ink repellent and supportive structure which may be used in conjunction with the teaching of U.S. Pat. No. 3,791,644 as well as further improvements which I have made in support and handling apparatus for handling freshly inked sheet material.